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41.
42.
I. D. Palmer 《Solar physics》1972,27(2):466-477
Two low-energy ( 1 MeV) solar proton events which display a gradual intensity increase to a maximum near the time of an SSC, followed by an abrupt, large decrease, are interpreted in terms of a population of cosmic rays which are swept ahead of an interplanetary shock wave. A model which describes the variation with time of intensity and anisotropy at the Earth is developed using a Monte Carlo technique which traces the histories of particles released impulsively at the Sun. A good fit to each of the profiles observed at 0.6 to 0.9 MeV proton energies is obtained with a diffusion coefficient 2 × 1020 cm2 s–) = 13.46 - 2.99 sin21 and a near perfect shock reflector.Now at University of California, LASL, Los Alamos, New Mexico. 相似文献
43.
44.
The electrical conductivity of the lunar interior has been determined from magnetic field step transients measured on the lunar dark side. The simplest model which best fits the data is a spherically symmetric three layer model having a nonconducting outer crust of radial thickness 0.03R
moon; an intermediate layer of thicknessR0.37R
moon, with electrical conductivity
1 3.5 × 10–4 mhos/m; and an inner core of radiusR
2 0.6R
m
with conductivity
2 10–2 mhos/m. Temperatures calculated from these conductivities in the three regions for an example of an olivine Moon are as follows: crust, < 440 K; intermediate layer, 890 K; and core, 1240 K. The whole-moon relative permeability has been calculated from the measurements to be/
0 = 1.03 ± 0.13. Remanent magnetic fields at the landing sites are 38 ± 3 at Apollo 12, 43 ± 6 and 103 ± 5 at two Apollo 14 sites separated by 1.1 km, and 6 ± 4 at the Apollo 15 site. Measurements show that the 38 remanent field at the Apollo 12 site is compressed to 54 by a solar wind pressure increase of 7 × 10–8 dynes/cm2.National Research Council Postdoctoral Associate. 相似文献
45.
Solar Physics - Possible mechanisms of the third harmonic generation in solar radio bursts are investigated. It is shown that the most essential is the coupling of plasma waves in a source with... 相似文献
46.
F. R. Allum R. A. R. Palmeira U. R. Rao K. G. McCracken J. R. Harries I. Palmer 《Solar physics》1971,17(1):241-268
Data obtained by the Explorer 34 satellite regarding the degree of anisotropy of ≳ 70 keV electrons of solar origin are reported.
It is shown that the anisotropies are initially field aligned, and that they decay to ≲ 10% in a time of the order of 1 hr.
The decays of the concurrent ionic and electronic anisotropies for one well observed event are in good agreement with the
diffusive propagation model of Fisk and Axford. The data suggest parallel diffusion coefficients for both ions and electrons
that are rigidity independent. From considerations of a long lived electron event, it is shown that the electronic fluxes
exhibit ‘equilibrium’ anositropies at late times. These are interpreted as indicating that convective removal at the solar
wind velocity is the dominant mechanism whereby solar cosmic ray electrons (∼- 70 keV) leave the solar system. They also indicate
that there is a positive density gradient at late times in a solar electron event. The data suggest that this was established
prior to the establishment of a similar gradient for the cosmic ray ions.
This research was supported by the National Aeronautics and Space Administration under contracts NASr-198 and NAS5-9075. The
research in India was supported by funds from the Department of Atomic Energy, Government of India and funds from the grant
NAS-1492 from the National Academy of Sciences, U.S.A. Support in data analysis was also provided by Air Force Cambridge Research
Laboratories, and by the Australian Research Grants Committee. 相似文献
47.
A multimodel comparison of centennial Atlantic meridional overturning circulation variability 总被引:1,自引:1,他引:0
Matthew B. Menary Wonsun Park Katja Lohmann Michael Vellinga Matthew D. Palmer Mojib Latif Johann H. Jungclaus 《Climate Dynamics》2012,38(11-12):2377-2388
A mechanism contributing to centennial variability of the Atlantic Meridional Overturning Circulation (AMOC) is tested with multi-millennial control simulations of several coupled general circulation models (CGCMs). These are a substantially extended integration of the 3rd Hadley Centre Coupled Climate Model (HadCM3), the Kiel Climate Model (KCM), and the Max Plank Institute Earth System Model (MPI-ESM). Significant AMOC variability on time scales of around 100?years is simulated in these models. The centennial mechanism links changes in the strength of the AMOC with oceanic salinities and surface temperatures, and atmospheric phenomena such as the Intertropical Convergence Zone (ITCZ). 2 of the 3 models reproduce all aspects of the mechanism, with the third (MPI-ESM) reproducing most of them. A comparison with a high resolution paleo-proxy for Sea Surface Temperatures (SSTs) north of Iceland over the last 4,000?years, also linked to the ITCZ, suggests that elements of this mechanism may also be detectable in the real world. 相似文献
48.
Richard P. Duncan Pavla Fenwick Jonathan G. Palmer Matt S. McGlone Chris S. M. Turney 《Climate Dynamics》2010,35(7-8):1429-1438
The warming trend over the last century in the northern hemisphere (NH) was interrupted by cooling from ad 1940 to 1975, a period during which the southern hemisphere experienced pronounced warming. The cause of these departures from steady warming at multidecadal timescales are unclear; the prevailing explanation is that they are driven by non-uniformity in external forcings but recent models suggest internal climate drivers may play a key role. Paleoclimate datasets can help provide a long-term perspective. Here we use tree-rings to reconstruct New Zealand mean annual temperature over the last 550 years and demonstrate that this has frequently cycled out-of-phase with NH mean annual temperature at a periodicity of around 30–60 years. Hence, observed multidecadal fluctuations around the recent warming trend have precedents in the past, strongly implicating natural climate variation as their cause. We consider the implications of these changes in understanding and modelling future climate change. 相似文献
49.
K. Uldall Kristiansen P. L. Palmer R. M. Roberts 《Celestial Mechanics and Dynamical Astronomy》2012,113(2):235-254
In this paper the importance of the ill-posedness of the classical, non-dissipative massive tether model on an orbiting tether system is studied numerically. The computations document that via the regularisation of bending resistance a more reliable numerical integrator can be produced. Furthermore, the numerical experiments of an orbiting tether system show that bending may introduce significant forces in some regions of phase space. Finally, numerical evidence for the existence of an almost invariant slow manifold of the singularly perturbed, regularised, non-dissipative massive tether model is provided. It is also shown that on the slow manifold the dynamics of the satellites are well-approximated by the finite dimensional slack-spring model. 相似文献
50.